The BCA information is used in digital versatile disk (DVD) Read Only Disk, for example, type A and C disks, as specified in standardized specifications such as the ECMA-267 specification, high definition (HD) Read Only DVD specification, Blu-Ray Disc specification, and the like. The BCA may be used for other formats. One of the primary purposes of providing the BCA to each format is copy protection. The information contained within the BCA region is used by the disk player to establish the software to be used in conjunction with the contents of that disk. The BCA information (or code) can be the same for a series of disks or unique for each disk. For example, the BCA information may specify a serial number of the disk so as to identify individual disks. The BCA information is typically recorded after the end of the disk manufacturing process.
FIG. 1 schematically illustrates a BCA 10 provided on an optical disk 12. The BCA 10 is an annular area inside of the lead-in area, typically at a radius about 22.3 mm to 23.5 mm. The BCA information is recorded using YAG laser after the main data content has been mastered on to the disk by the manufacturer. The information is “cut” into the reflective layer of the finished disk. The BCA information may also be recorded by means of replication process (stamping), for example, using embossed pits. The BCA information is written with a series of low reflectance stripes (or pits) arranged in circumferential direction and extending radially within the BCA region.
Conventionally, disk players read the BCA by rotating at a constant angular velocity (for example, 1440 rpm), moving the optical pickup unit (OPU) to the BCA area, focusing on the information surface, and using a special decoding circuit for the BCA signal which has a frequency much lower than a normal DVD high frequency (HF) signal. Typically, conventional solutions use dedicated hardware including some form of defect detection to extract the BCA channel data. Typically, the marks in the BCA are detected as a drop-out in the HF signal. Since the frequency of BCA signal is different from that of the normal DVD HF signal, additional hardware, such as phase lock loop (PLL) circuitry, is used to perfrom timing and data recovery on the extracted BCA data. Then, data formatting and error correction process (for example, using the Reed Solomon code) are performed on the BCA data to obtain the data contents.